As one knowledgeable in the art will be well aware, a typical septic system is founded on a tank in which wastes are collected, settled, and partially digested. The septic tank leeches what is termed gray water into a drain field where it is dispersed. When the system is operating properly, the dispersed gray water will be substantially devoid of solid matter. When the system is not operating properly and solids are suspended in the gray water, the drainage field can become clogged by solids such that the gray water ceases to be absorbed and dispersed properly thereby resulting in drainage field failure. With this, ground and surface water can become polluted, and the system can otherwise malfunction.
When operational, a septic tank has three biologically active zones that are commonly referred to as an upper, cake or scum layer, a middle, liquid zone, and a bottom, sedimentary or sludge layer. Waste matter enters the liquid zone at the middle of the tank. The sedimentary layer is formed as heavy solids settle to the bottom of the tank as sediment, or sludge, where they are further decomposed. Some of the sediment, however, will not be biodegradable and will remain at the bottom of the tank. The cake layer is formed as fats and other lighter suspended solids rise to the top of the tank where they too may further decompose.
During proper septic tank operation, only material from the liquid zone is dispensed to the drainage field. The effective volume and rate of flow of the tank determine the tank's settlement rate. The volume of the tank's liquid zone, therefore, is considered the tank's effective volume. In turn, that effective volume is used to determine the fixed design capacity of the tank, which is measured as the ability of the tank to process a particular flow rate of material. With this, the tank will be unable to process material entering the system at an inflow rate over the maximum allowable flow rate.
A septic tank's system capacity, on the other hand, is condition dependent in that it is indicative of the system's ability to continue to process material. The tank's system capacity falls to zero when, for example, particles of the sedimentary or cake layers begin to escape from the tank to the drainage field or the sedimentary and cake layers become so close to one another that the liquid layer is nearly or completely extinguished.
Advantageously, as a result of anaerobic decomposition in the upper and bottom layers, the increase in thickness of the sedimentary and cake layers is substantially less than the rate at which corresponding solids are input into the system. Nonetheless, the bottom, sedimentary or sludge layer and the upper, scum or cake layer do tend to increase progressively in thickness during normal operation of the septic system such that the accumulated solids must eventually be pumped from the system.
Common practice suggests that this pumping be carried out when the volume of the middle liquid zone is reduced to roughly one-third of the total height of the three layers. When that need for pumping will be reached, however, is dependent on the mix and overall volume of waste that is input to the system and the effectiveness of the biological decomposition occurring in the septic tank. Pumping may be considered necessary based on the absolute location of the top layer, the absolute location of the bottom layer, or a combination of these factors that have reduced the volume of the middle, liquid zone to a given extent. Notably, as the volumes of solids increase in the septic tank, the effectiveness of the biological decomposition tends to increase thereby leading to a decreased rate of accumulation even with a constant input rate. With this, it will be appreciated that the required pumping interval is substantially unpredictable and can range from as little as two years to as much as fifteen years and longer.
A major difficulty in septic tank operation is that, because it is necessarily carried out underground, the status of the septic tank is generally difficult or impossible to perceive. With this, the first indication of a failure in the system often comes in the form of the unpleasant backup of waste material into the associated home or building. Even more disadvantageously, this backup occurs typically well after the system has begun to discharge substantial solids into the drainage field.
Advantageously, a number of methods and systems have been disclosed by the prior art for providing an indication as to whether a given septic system is in need of pumping. One most basic means is by digging up and removing the access cover for the tank and dipping what is termed a flapper stick into the tank to gain an estimation of the height of each of the layers. As one will appreciate, this is a cumbersome and unpleasant practice and is often done merely to confirm that an already-occurring failure is in fact due to a need for pumping.
Other systems have been disclosed that are intended to allow a septic tank operator to monitor the contents of the tank without the need for manually opening the tank and interacting with its contents. For example, relatively simple mechanical devices have been disclosed wherein, for example, a float within the tank is coupled to an arm that projects from the tank to indicate the status of one or more layers within the tank. Other, more complex systems have been disclosed with elongate sensing probes for being permanently disposed in a septic tank. Sensors disposed along the probes have been of a wide variety of types including sonic sensors, light emitting and detecting sensor combinations, electrical resistance sensors, and still other sensor arrangements.
Unfortunately, even these improved systems and arrangements have left septic tank operators with a number of disadvantages and shortcomings. By way of example and not limitation, one knowledgeable in the art will be aware that many prior art systems are vulnerable to malfunction and fouling as they spend years disposed within a septic tank. Furthermore, prior art systems often are incapable of providing the septic tank operator with consistently accurate information regarding the status of the contents of the septic tank. Still further, some systems are simply incapable of taking accurate readings or readings of sufficient resolution while others additionally or alternatively cannot relay taken readings accurately or with sufficient resolution from the system to the operator. In light of these and further disadvantages of the prior art, it becomes clear that there remains a need for a septic tank monitoring system and method that overcomes these and other shortcomings of the prior art while providing a number of heretofore unrealized advantages thereover.